How is Antigone different from a classical greek tragedy?

A traditional Greek tragedy, according to Aristotle, has
to be a tightly unified play based on a single action and featuring a single
protagonist. In addition, this tragic hero suffers a downfall because of some error of
judgement or frailty rather than a vice or some form of depravity. Thus it is that
Macbeth for example can be said to be a tragedy because of
Macbeth's ambition and how it brings his downfall.

However,
when we think of these categories, Antigone does not exactly fit
the mould of such a Greek tragedy. First of all, Antigone herself does not occupy much
of the play. She is a character who is desposed of quickly by Creon. Secondly, it is
hard to detect what her tragic flaw is, unless it is her resolute belief that the Gods
and family should be honoured above the law of the land. She indeed does suffer a
terrible end for this adherence to a higher law, and is undoubtedly a tragic character
in the way that she laments about never being able to be a wife, but at the same time
she doesn't seem to fit the description of a tragic hero or heroine according to
Aristotle.